Disabling automatic member failback

In some situations, you might want to delay the automatic failback, this is done through the db2cluster command.

About this task

By default, Db2® cluster services fails back any member running in restart light mode as soon as that home host of member becomes available and any alerts are cleared. If you want to investigate the cause of a host failure, it can be useful to disable automatic member failback until a more suitable time.

Procedure

To disable automatic failback:

  1. Log in as an instance user and issue the db2cluster command: 
    db2cluster -cm -set -option autofailback -value off
  2. Restart the Db2 pureScale® instance.

Results

Any member that is in restart light mode and any future restart light members will remain on their guest host until all member alerts have been cleared explicitly and the resident host of the member is active.

Example

After experiencing a repeated host failure that resulted in members being restarted in light mode, the DBA decides that it is better to keep any failed hosts free of their resident members until the cause of the failure can be determined. The DBA issues the command: 
db2cluster -cm -set -option autofailback -value off
This message is returned:
The db2cluster command succeeded. The AUTOFAILBACK option has been set to "OFF". Automatic 
failback will be disabled the next time that the Db2 database manager instance is restarted.
Note: If, for some reason, automatic failback had already been disabled, the command would have successfully completed, but the message will not mention restarting the instance.
The DBA restarts the instance. After investigating the cause of the host failure, the DBA issues the command to turn on the automatic member failback:
db2cluster -cm -set -option autofailback -value on
This message is returned:
The db2cluster command succeeded. The AUTOFAILBACK option has been set to "ON". Automatic 
failback will be enabled the next time that the Db2 database manager instance is restarted.
After restarting the instance, the DBA ensures that automatic member failback is enabled using the command:
db2cluster -cm -list -autofailback
This message is returned:
The AUTOFAILBACK option is set to "ON".